A Comprehensive Mixed-Mode Time-Domain Load- and Source-Pull Measurement System

Abstract

We present a novel test set devised for nonlinear balanced device characterization using load-pull techniques. The system is capable of measuring the voltage and current waveforms at the calibration reference planes while independently tuning the device under test (DUT) source and load differential-and common-mode terminations. The test set is designed to address present and future large-signal multiport measurement needs, easing the characterization task while developing new multiport active devices.

Mixed-Mode Active Load-Pull Using one Single-Ended Device-Under-Test

“…The starting point is the well known formulation [12] of 2-port mixed-mode S-parameters S mm and its standard 4-port S-parameter equivalent S.…”

“…From the waves around the DUT: a 1 and b 1 at the input and a 2 and b 2 at the output (Fig. 2), the common and differential waves of the mixed-mode formulation can be calculated [12]:…”

On different load configurations for mixed-mode load-pull measurements, hybrid imperfections, and tuning ranges

“…In this sub-section, we assumed that the connection network S ′′′ c is an ideal 180°hybrid as defined in (5). The results from (6) to (8) show that differential and common mode reflection coefficients are independent of each other, and reduce to the reflection coefficients of the tuners. Mode conversion is zero for an ideal 180°hybrid.…”

“…The mathematical expressions derived using this approach are too complex to be readable and informative, thus we used plots to visualize their meaning. For this discussion, the differential input ports of the 180°hybrid are port 1 and port 2, the difference port is port 3, and the sum port is port 4, as it was already defined in (6). For demonstration of the impact, we chose a reflection coefficient of S S = 0.6 /20 • for the common mode tuner and a reflection coefficient of S D = 0.8 /w with w = 0…360°for the differential mode tuner.…”

“…Other approaches (compare [4,5]) use 180°hybrids also at the output of the device, but only to tune the differential mode load. Mixed-mode loadpull measurement setups able to independently tune the loads of both, the common mode and the differential mode component of the output signal, were proposed in [6] and [7].…”